The present invention relates to a spring device and more particularly to a spring device of the type used in automatic transmissions for motor vehicles.
Automatic transmissions for vehicles often include a plurality of coil springs that are adapted to apply a biasing force against clutch plates that control the engagement of various gears in the transmission. These coil springs are assembled in a ring shaped device comprising two annular plates having a multiplicity of circumferentially spaced, parallel compression coil springs mounted therebetween. Such a ring shaped spring device is disclosed in Orlowski 5,306,086, which is incorporated by reference herein as the basic background to which the present invention is directed.
In the ring shaped spring device disclosed in Orlowski 5,306,086, there is a pair of spaced apart first and second annular support plates defining the ring shape of the spring device. A plurality of circumferentially spaced parallel oriented coil springs are disposed between the annular plates so that vertical movement of one plate toward the other compresses the springs. To interconnect the plates, an integral hook is formed in one plate and a loop is integrally formed in the other plate. The hook and loop are designed so that the device can be assembled by merely locating the various coil springs and then pressing one plate toward the other. The hook snaps over the loop to lock the plates together, with the coil springs partially compressed. However, when assembled in a transmission, the ring shaped spring device is compressed further so that the hook actually disengages the loop. Consequently, during repetitive operation of the spring assembly over many years, the individual coil springs can become canted in a manner to reduce the spring constant and cause damage and/or unintended biasing forces. By compressing the spring device for shifting the gears of the automatic transmission, distortion of the coil springs in the annular direction is magnified. Consequently, the prior ring shaped spring device, as shown in Orlowski 5,306,086 only employs the concept of integral interconnecting means and does not address the problem of controlling the annular movement of the spaced plates during long term operation of the spring device.
The present invention relates to a ring-shaped spring device as shown in Orlowski 5,306,086, wherein there are a plurality of guide assemblies located at circumferentially spaced positions around the ring. Each of these guide assemblies includes a first tab extending from one of the plates toward the other plate, a second tab extending in the opposite direction from the other plate to form a generally sliding contact between the first and second tabs as the spaced plates move vertically to compress and release the coil springs. The first tab has a guide slot with a given width. The slot extends in a direction perpendicular to the plates. The second tab carries an assembled elongated guide member extending radially through the guide slot to positively guide the vertical movement between the two plates. There is no integral interconnecting means, since the two tabs of the plates are joined together by a third member which is an assembled elongated guide member. The guide slot has an end remote from the plate from which the second tab extends. The distance of this end from the plate causes compression of the coil springs by the action of the guide member when the device is assembled. Thus, the springs are positioned between the two annular plates and the plates are oriented with the spaced tabs of one plate in sliding contact with the spaced tabs on the other plate. The springs are then compressed and the elongated guide member is press fitted through one tab and extends into the guide slot of the other tab. To support the guide member, the second tab includes a bore defined by an extruded boss that allows a press fit of the guide member in the boss to maintain the guide member in the proper horizontal position. The structure assembly procedure and operation of the present invention is different than the ring shaped spring device in Orlowski 5,306,086. These added features result in the advantage of being capable of maintaining the proper annular orientation between the spaced plates during long term operation of the spring device in an automatic transmission.
In accordance with another aspect of the present invention, there are an even number of guiding assemblies around the circumference of the matching annular plates. One group of guide assemblies has the first tab extending from the first plate and the second group has the first tab extending from the second plate. By using two groups of guide assemblies, the tabs of a plate alternate between a tab with the guide slot and a tab with the guide member. The tabs are integrally formed in the guide plates so the two plates are identical. In the preferred embodiment, four guide assemblies are used with the integral tabs at the twelve o""clock position and six o""clock position having one construction and the tabs at the three o""clock position and nine o""clock position having the opposite configuration. By merely indexing the plates 90xc2x0, identical plates can be used in constructing the ring shaped spring device.
Another aspect of the present invention involves extending tabs to locate the coil springs around the annular plates. These spring locating tabs are lanced from the edge of the plates and are bent downwardly at circumferentially spaced locations around the ring. The edge lanced tabs are bent downwardly from a position generally the midpoint of the plates, whereby the coil springs are located by the tabs in the center of the spaced plates. In this manner, a punch press operation can merely lance and bend the tabs for locating the coil springs circumferentially around the plates. The tabs are easily formed from the plates by a simple bending operation as opposed to the complex bending operation required in Orlowski 5,306,086.
The primary object of the present invention is the provision of a ring-shaped spring device having two annular plates used to capture and locate circumferentially spaced coil springs, which spring device guides the movement of the annular plates as the springs are compressed or released.
Another object of the present invention is the provision of a spring device, as defined above, which spring device uses a separate pin in a slot to control the movement of a tab on one plate with respect to a sliding tab on the other plate.
Yet a further object of the present invention is the provision of a ring-shaped spring device wherein spaced annular plates are held together by guide assemblies having members that limit the movement between the plates to a generally vertical sliding movement as the plates move vertically to compress and/or release the coil springs.